Secondary-emissive electrode

ABSTRACT

A secondary emissive electrode for image intensifiers, cathoderay tubes and the like which comprises a plate of insulating material having two substantially parallel boundary surfaces on opposite sides thereof pierced by channels, the walls of which are secondary emissive, forming a high-density network of channels between two surfaces. The periphery of this plate has at least two regions one opposite the other relative to the center of the body with channels which are filled with a core material. In the manufacture of such an electrode, all channels are initially filled with a material which can be etched away by an acid. Those channels in the regions of the periphery are covered with a coating which is etch resistant, and the core material in the remaining channels etched away after which the coating is removed.

llriite tates tent Qlement 451 Sept. 19, 1972 [54] SECONDARY-EMISSIVE ELECTRODE [72] Inventor: Gerard Clement, Pairs, France [73] Assignee: U.S. Philips York, NY.

[22] Filed: Feb. 16, 1971 [21] App]. No.: 115,637

Corporation, New

[30] Foreign Application Priority Data April 6, 1970 France ..7012321 [52] US. Cl ..3l3/103, 313/95 [51] Int. Cl ..H0lj 43/02 [58] Field of Search .313/103, 104, 105, 95

[56] References Cited UNITED STATES PATENTS 3,440,470 4/1969 Decker ..313/103 3,492,523 1/1970 Smith et a1 ..3 13/105 3,609,433 9/1971 Freedman ..313/95 Primary Examiner-John S. Heyman Att0rney-Frank R. Trifari [57] ABSTRACT A secondary emissive electrode for image intensifiers, cathode-ray tubes and the like which comprises a plate of insulating material having two substantially parallel boundary surfaces on opposite sides thereof pierced by channels, the walls of which are secondary emissive, forming a high-density network of channels between two surfaces. The periphery of this plate has at least two regions one opposite the other relative to the center of the body with channels which are filled with a core material.

In the manufacture of such an electrode, all channels are initially filled with a material which can be etched away by an acid. Those channels in the regions of the periphery are covered with a coating which is etch resistant, and the core material in the remaining channels etched away after which the coating is removed.

3 Claims, 4 Drawing Figures PATENTEDSEP 19 I972 Fig.4

INVENTOR.

AGENT SECONDARY-EMISSIVE ELECTRODE This invention relates to a secondary-emission electrode of the channel plate type for use in electronic tubes, said electrode being formed by a glass body or a body of similar material having two substantially parallel boundary faces and traversed by micro-channels forming a high-density network between said two faces.

The density of the aforesaid channels may be channels/cm each channel having a diameter of about 10y" Various methods are used for manufacturing such matrices. One of them consists in drawing a fiber of two kinds of glass, one type of soft glass formingthe core and the other type being a harder glass forming the sheath.

After drawing the fiber is cut into sections and the various sections are pressed against each other and heated, if desired, after the insertion of a melt ensuring the adhesion between the tubes. The central glass is then dissolved by an acid and then the channel plate is covered on both faces with a conductive layer.

The glass core serves for preventing deformation of the channels, when the sections are stuck to each other, which gives rise to pressure on the tube walls. Instead of the glass cores metal wires may be employed.

- The channel plate or secondary-emission electrode is suitable for being mounted in an electronic tube, for example, an image intensifier or a cathode-ray tube.

Since in order to ensure a normal operation of this electrode it is necessary to apply between the two faces a voltage difference of the order of 1 kV, for example, it is common practice to hold the plate in position by metal rods, which also serve as electrodes. It is generally endeavored to hold the plate on the smallest possible plate surface in order to obtain a large operative surface.

This disposition gives rise to two drawbacks. The first is of mechanical nature. The feeding electrodes have to hold the whole weight of the plate and grip only a few hollow channels. This involves the risk of breakage of channels, due to which the tube may become unserviceable. The second drawback is of an electro-optical nature. Even in the absence of incident electrons on the input face, the contact between the electrodes and these channels may produce field emission by point effect. The electrons thus released are amplified in the channel and on the phosphor screen or the photo graphic plate they produce fixed luminous points producing parasitic light, which may be harmful to the study of given phenomena.

The present invention has for its object to obviate these drawbacks.

According to the present invention the secondary emissive electrode of the channel type for use in electronic tubes is formed by a body a plate of insulating material having two substantially parallel boundary faces and pierced by channels forming a high-density network between said two faces, the inner surfaces of said channels being secondary-emissive. The periphery of this plate has at least two regions one opposite the other relative to the center with channels filled with a core material.

According to a further feature of the invention the zone having the filled channels forms a peripheral crown.

A matrix or channel plate of this type provides furthermore the advantage of an improved distribution of the voltage applied between the input and output faces.

The invention has furthermore for its object to provide a method of manufacturing such a plate. This method consists in coating the periphery of the plate or given zones of the peripheral crown with varnish or any other readily soluble product, which is soluble in conventional solvents but which is resistant to the acids used for attacking the cores or centers of the channels.

This operation is carried out after the tubes have been glued, after polishing of the faces and prior to the dissolution of the cores. When the cores of the channels are of metal, partial dissolution is carried out in the zones which will remain filled in order to avoid shortcircuit between the faces of the channels, where the voltage is applied.

The invention will be better understood from the description of the Figures, which show:

FIG. 1 a front view of a plate in accordance with the invention,

FIG.2 a side elevation of the same plate taken along the axis I I,

FIG. 3 a front view of a further embodiment,

FIG. 4 the circuit diagram of an image intensifier provided with an electrode embodying the invention.

For the sake of clarity and'for practical reasons the channels shown are not drawn to scale.

The plate 1 shown in FIG. 1 has a circular section. A crown 2 is protected against the attach of the core material to form the channels. This protection may be obtained by applying a collodium layer, forexample, by means of a brush, while the plate is still formed by filled sections.

The plate is introduced into a support for centering the applied collodium layer, after which etching is performed; the assembly is then immersed in acetone, which cleans the plate and dissolves the collodium.

As an alternative a layer of plastic material or of teflon may be used.

The two faces of the plate are then provided by vacuum-evaporation or cathode sputtering with a metallic layer, for example, of nickelchromium.

In FIG. 1 the layer is omitted to show that the final electrode is formed by filled channels 4 and hollow channels 5, the former constituting the region 2.

From FIG. 2, which is a sectional view of the plate of FIG. 1 taken on the line I I, it will be seen that a metallic layer 6 serves for applying the voltage between the two faces of the plate.

FIG. 3 illustrates a further method of carrying out the invention, in which only sectors 2 of the plate are protected from the etchant of the core material.

This Figure also shows electrodes 7, which form supports for the plate. This disposition may be advantageous, when it is desired to obtain a large operative surface. As a matter of course, the number of zones 2 is arbitrary and the voltage may be applied to a single electrode.

FIG. 4 shows an image intensifier, in which the plate 1 is mounted between a photo-cathode 8 and a phosphor screen 9. The plate is held by the electrode supports 7, which are connected to the respective terminals of a direct-voltage generator 10.

core material.

2. An electrode as claimed in claim 1, wherein said zones with filled channels constitute a peripheral crown.

3. A method of manufacturing a secondary-emissive electrode comprising the steps of coating a peripheral portion of a plate having channels filled with a core material with an acid-resistant cover, thereafter etching away with an acid the core material filling said channels outside said peripheral zone which are uncovered, and thereafter subsequently dissolving said cover. 

1. A secondary-emissive electrode comprising a body of insulating material Having two substantially parallel boundary faces on opposite sides thereof and being pierced by channels forming a high-density network between said faces, electrode means on each of said boundary surfaces, the walls of said channels being secondary emissive, and the periphery of said plate having at least two zones opposite one another relative to the center of said plate having channels filled with a core material.
 2. An electrode as claimed in claim 1, wherein said zones with filled channels constitute a peripheral crown.
 3. A method of manufacturing a secondary-emissive electrode comprising the steps of coating a peripheral portion of a plate having channels filled with a core material with an acid-resistant cover, thereafter etching away with an acid the core material filling said channels outside said peripheral zone which are uncovered, and thereafter subsequently dissolving said cover. 